We used the \(\ell _1\)  periodogram, a compressed-sensing method developed by [1]}, to identify the sparsest set of orbital periods that could simultaneously fit the scalpels shift signal. The resulting sparse solution eliminated unwanted alias signals and revealed three dominant candidate signals. This analysis favoured the results from the scalpels projection, that CoRoT-7 is better modelled as a 3-planet system than a 2-planet system. Because the \(\sim \) 23-d signal varies slowly in phase and amplitude, we noted the usefulness of a split-period representation for reproducing the detailed frequency structure of the periodogram and for determining the orbital velocity amplitudes of the three dominant planet signals.
